As part of the constant evolution of the GSM/EDGE Radio Access Network (GERAN), the legacy GSM/EDGE receiver has been enhanced by the Downlink Advanced Receiver Performance (DARP) technologies that are being standardized by the 3GPP.
The so-called legacy receiver is a one antenna receiver that applies to 8 PSK (8 phase shift keying) modulation and GMSK (Gaussian Minimum shift keying) modulation.
One of the advanced technologies is referred to as Single Antenna Interference Cancellation (SAIC). This has been implemented in the so-called DARP-I receiver that is already in the 3GPP TS 45.005 standard. This approach only applies to GMSK (Gaussian minimum shift keying) modulation. The RF receive chain is substantially the same as in the legacy receiver featuring a single antenna. However, some advanced signal processing techniques are employed to make the receiver appear to have multiple antennas, referred to as virtual antennas since in fact there is only one physical antenna. This is achieved in part by over-sampling the received signal. More specifically, two samples per received symbol are taken instead of just one.
Another of these technologies is referred to as Mobile Station Reception Diversity (MSRD), and this is in the final phase of the standardization. This approach uses two receive antennas, and applies to both 8-PSK and GMSK modulations. Over-sampling is also performed with this approach.